The present invention relates to a transmission equipped with an auxiliary speed changing gear.
The transmission of the kind mentioned above is usually used in such a heavy-duty vehicle having an engine the power of which is relatively small for the heavy load of the vehicle, in order to ensure a sufficiently high running performance of the vehicle assisting the small power of the engine.
In case of so-called front engine and front-wheel driving type vehicles and so-called rear engine and rear-wheel driving type vehicles in which the installation space for the transmission is extremely limited, it is necessary to provide an additional gear shaft, for constructing an auxiliary speed changing gear. This additional gear shaft inconveniently incurs increase of installation space, weight of the transmission and the cost of the vehicle. For this reason, the transmission having an auxiliary speed changing gear could not be used successfully in small-sized vehicles of the above mentioned type.
In order to make the minimized fuel consumption rate and the sufficiently high running performance compatible with each other, over various running modes including expressway-cruising, negotiating urban traffic snarls, hill-climbing and descending in mountainous areas, the number of speed changing ratios to be performed by the transmission has to be as large as 6 to 10. The shifting operation with a transmission having such a large number of speed changing ratios is extremely troublesome.
In case of passenger cars, the output power of the engine is sufficiently large, so that the transmission may be shifted two stages, i.e. skipping over the intervening gear.